Heat-resisting nickel base alloys



United States Patent HEAT-RESISTING NICKEL BASE ALLOYS Clarence GeorgeBieber, Bayonne, NJ., assignor to The International Nickel Company,Inc., New .York, N.Y., a corporation of Delaware No Drawing. Filed Aug.22, 1955, Ser. No. 529,926

27 Claims. (c1. 75-171) The present invention relates to special hightemperature, heat and stress resisting thermal members which aresubjected in use under stress at elevated temperatures to destructiveactions of various media, especially to the corrosive action of suchmedia as oxidizing, neutral and reducing atmospheres containing harmfulconstituents, and to special heat resisting, columbium-free andtungsten-free, nickel-chromium alloys suitable for use as such thermalmembers. i

Heretofore, the art has endeavored to produce satisfactory hightemperature alloys for use as heat and stress resisting thermal membersin such heat engines as gas turbines, jet engines and the like. Whilemany alloys 'have been proposed, continual demands by industry for heatengines with higher speed and power capacity have placed more rigorousrequirements on thermal members of heat engines, including therequirement that thermal members withstand higher and higher operatingtemperatures under higher and higher stresses. In addition, such heatand stress resisting thermalmembers must possess, among other things,resistance to creep and resistance to corrosion, erosion, oxidation andpitting'at elevated temperatures as well as being capable of resistingdestructive actions of operating media. Under operating conditions,thermal members of gas turbines and jet engines are subjected to varioustypes of stresses, including not only steady or static stresses but.also fluctuating or alternating dynamic stresses which complicate theproblem of providing satisfactory alloys for use as thermal members, forexample, turbine blades, valves and valve parts, and other componentparts of heat engines and the like.

In evaluating alloys for high temperature properties, stress rupturetests at elevated temperatures are usually relied upon. Such a test cancomprise subjecting a test specimen of the alloy to a rupture test at atemperature of 1500 F. under a given stress. The time it takes thespecimen to rupture, i.e., ts rupture life, under the foregoingconditions is employed to evaluate its behavior under stress in service.It has been proposed that cast alloys be employed in a number ofinstances but it has been found that the cast alloys had thedisadvantage of varying widely in fatigue and creep properties amongdifferent castings of the same alloy. Furthermore, .certain types ofboron-hardened cast alloys were proposed for use as blade material butwere found not completely A 2,971,222. Patented Mar. 28, 19stsatisfactory, particularly because the alloys were usually glass brittleat'room temperature and were highly sensitive to breakage in handlingand also very sensitive to thermal shock. For these and a number ofother reasons, it became necessary to employ'thermal members made ofWrought alloys in many applications. In searching for satisfactorywrought alloys, for example, alloys having a high rupture life at higherand higher temperatures, the art found that it was necessary toincorporate in the alloy very substantial amounts of certain specialalloying elements. Under existing world conditions, the art became morecognizant of the fact that a shortage-existed in certain importantalloying elements and this led to the classification of these scarcealloying elements as strategic elements. Columbium is considered themost strategic alloying element. The other important strategic but lessscarce alloying elements are tungsten and cobalt. While still otheralloying elements might be deemed strategic elements, these otherelements are much more plentiful and much less strategic. The termstrategic elements, as employed herein, refers to the highly strategicelements columbium,'tungsten and/or cobalt. In the search for wroughtalloys of exceptionally high properties at elevated temperatures, it wasfound that the more satisfactory wrought alloys usually contained two oreven all three of the aforementioned strategic elements in substantialamounts. Many of these more satisfactory wrought alloys required thepresence of the particularly strategic element columbium in an amountwhich created a potential demand for columbium far exceeding theavailable supply. A number of alloys required the use of colum biumand/or tungsten in combination with cobalt. In vie-w of the situationrequiring the minimum use of strategic elements, the art was placedunder pressure .to provide wrought alloys having a high fracture lifeof,

at least about 150 hours when tested at the relatively high temperatureof about 1500 F. under the high stress for this temperature ofabout30,000 pounds per square inch (p.s.i.) and being suitable for useas therm al'mernbers, for example, in jet engines, which must withstandhigh stresses at temperatures of the order of 1300 F.

to 1700 F., particularly temperatures of the order of 1500 F. to 1700 R,such as are encountered when a plane is operated under condition-srequiring high speed and/or power. Although many attempts were made toovercome the foregoing difficulties and other difficulties anddisadvantages, none, as far as I am aware, was entirely successful whencarried into practice commercially on an industrial scale.

It has now been discovered that the problem confronting the art ofproviding a high temperature, heat and stress resisting thermal memberhaving a high level of high all-around properties can be solved byemploying a special heat resisting, columbium-free, tungsten-free,nickel-chromium alloy containing a combination of elements withinspecial ranges and capable of being fabricated into wrought form by hotworking and cold working operations. I

It is an object of the present invention to provide an improved alloyhaving improved high temperature properties and not requiring thepresence of a plurality of strategic alloying elements and particularlynot requiring the presence of the extremely strategic alloying elementcolumbium. Another object of the invention is to provide improvedheat-treatable, nickel-chromium, high temperature, heat and stressresisting, wrought thermal members suitable for use in jet engines, gasturbines and the like. v The invention also contemplates providingimproved heat treated, nickel-chromium, high temperature, heat andstress resisting, wrought thermal members characterized by resistance tothe destructive actions of various operating media at high temperatures.

It is a further object of the invention to provide an improved heat andstress resisting, high temperature, nickel-chromium alloy which, in aheat treated, wrought condition, neither requires the presence of thehighly strategic alloying element columbium nor the presence of aplurality of strategic elements to achieve a high rupture life of atleast about 600 hours, and even 1000 or 1500 hours or more, under astress of about 30,000 p.s.i. at 1500 F., and a rupture life of at leastabout 100 hours, and often at least 200 or even 250 hours or more, undera stress of about 25,000 p.s.i. at 1600" F.

It is still another object of the invention to provide .acolumbium-free, tunsten-free, heat resisting, Wrought nickel-chromiumalloy which is characterized by a level of high temperature propertiesin a heat treated condition comparable to or even better than theproperties of other wrought alloys containing columbium or a pluralityof strategic elements.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the present invention provides a novel hightemperature, heat and stress resisting thermal member especially adaptedfor use in heat engines and the like, e.g., jet engines, gas turbines,turbo-superchargers and exhaust gas power-recovery turbines, which ismade of a special nickel-chromium-molybdenum-aluminum titanium alloy,which does not require the presence of either of the strategic elementscolumbium and tunsten and which possesses commercial hotandcold-workable properties enabling its fabrication into wrought members.

The alloys within the scope of the present invention broadly compriseabout 5% to 18% or 20% chromium. about 1% to 10% molybdenum, up to about40% cobalt. about 0.05% to 0.35% carbon and an aluminum plu titaniumcontent of about 3.5% to 8.5% with the ratio of aluminum to titaniumbeing between about 0.5 :1 and about 3:1. not more than about 5% ironand with the balance being essentially nickel. By varying the composi-'tion of the alloy within the aforesaid ranges, it is possible to obtainvarious combinations of properties in castings and/r heat treatedwrought products. Thus, with a chromium content within the range ofabout to about 9% and an aluminum plus titanium content of about 5.5% toabout 8.5% and less than 10% cobalt, a high level rupture life,especially at high temperatures of the order of 1700 F. to 1800 F.. isgenerally obtained without using large amounts of cobalt. However. byemploying larger amounts of cobalt from about 10% to 40%, improvednotched strength at temperatures of the order of about 1350" F. isobtained. In order to provide optimum high temperature strength,including high rupture life at temperatures on the order of about 1500F., 1600 F. or higher, the alloys contemplated in accordance with theinvention may contain minor amounts of boron and zirconium with theboron content ranging from a few ten thousandths of a percent up toabout 0.009%, e.g., 0.0002% to 0.009%, and with the zirconium contentbeing within the range of about 0.01%

to about 0.25%. No further improvement in high temperature properties isfound in wrought alloys when the boron and zirconium are increased abovethe foregoing amounts and it is found that the forging temperature rangeis undesirably restricted. The balance of the alloy is nickel and thenickel plus cobalt content is usually about 50% to about of the alloy.The term balance" as used herein includes small amounts of otherincidental elements and impurities commonly present in nickel alloys,for example, silicon, manganese, copper, magnesium, etc. As will beappreciated by those skilled in the art, small amounts of otherelements, such as vanadium, cerium, tungsten, etc., may be added to thealloy for purposes well known in the art, including grain refinement,malleabilization, strengthening, etc. With regard to the silicon andmanganese contents, it is preferred that each of these elements shouldnot exceed 1% of the alloy content and each should more preferably bemaintained below 1% although manganese can be as high as 2% or even 3%and silicon as high as 2%. The copper content of the alloy should bemaintained below 2% and preferably below about 0.5% or 1%. Magnesium mayadvantageously be present in small amounts, e.g., 0.002%, up to about0.1%. Impurities, such as lead, bismuth, tellurium, sulfur, selenium,arsenic, antimony. etc., should be kept as low as is commerciallypracticable. It is preferred that the impurities lead, bismuth andtellurium be held to 0.01% maximum of each while sulfur, selenium,arsenic and antimony are preferably maintained below 0.05 and morepreferably below 0.02%, of each. When the alloy contemplated by thepresent invention is characterized as being colurnbium-free andtungsten-free, it is to be understood that this characterization isintended to denote that the strategic elements columbium and tungstenmight not be present or deliberately added to achieve the propertiesdescribed herein. As will be appreciated by those skilled in the art, itis not intended to exclude the presence of either or both of theseelements as an incidental element introduced With the raw materialsemployed to produce the alloy. to treat the molten bath of the alloy,etc. A feature of the alloy provided by the present invention is thefact that the presence of these elements is not required to achieve theproperties indicated herein.

The aforedescribed alloys contemplated in accordance with the inventionmay be hot worked. e.g., by forging, rolling, extruding, etc., into thephysical form of thermal members. When desired. thermal members producedin these alloys can be cast directly to shape. In such cases, the boroncontent of the alloy may be increased to as much as about 0.02%, e.g.,about 0.0002% to about 0.02%, and the carbon content may be increased toas much as about 0.5%, e.g., about 0.05% to about 0.5%, with theremainder of the alloy consisting of elements in the ranges set forthhereinbefore. The boron content of the castings should not exceed about0.02% as otherwise difficulties in welding are encountered. When thecarbon content exceeds about 0.5%, it is found that the strength of thecastings is detrimentally affected.

Preferably, the aluminum plus titanium content of the alloyscontemplated by the present invention will lie in the range of about 5%to about 7% when optimum rupture strength at the service temperature isrequired. For maximum ductility at the service temperature, the aluminumplus titanium content preferably will be about 4.5% to about 6%. Ineither of these preferred cases, the ratio of aluminum to titaniumpreferably will be about 0.821 to about 1.611.

When alloys produced in accordance with the invention are employed inthe form of fabricated thermal members heat engines and the like, it ispreferred that the wrought alloys be subjected toaheat treatmentcomprising a high temperature heating in the temperature range of about2000 F. to about 2400 F. for about at least A hour up to about 8 hours,e.g., about 2 hours, cooling rapidly, e.g., as by air cooling orquenching, and then reheating for at least 1 hour within the temperaturerange of about 1350 F. to 1800" F. for a period of time notsubstantially exceeding about 48 hours, e.g., about 4 hours to 24 hours.In general, the temperature employed for the high temperature heattreatment should be increased toward the upper part of the heating rangewhen the aluminum plus titanium content of the alloy is about 5% or morein order to provide the best high temperature properties for theparticular alloy. It is also to be noted that the optimum temperature tobe employed in the high temperature heating is influenced by thecomposition and characteristics of the particular alloy being heated.For example, in the high temperature heating, undesirable coarsening ofthe grains may result. Those skilled in the art will appreciate that theheat treatment, when applied to wrought alloys, may be applied entirelyafter the alloy has been fabricated into thermal members or may beapplied partly before fabrication or during fabrication or partly afterfabrication. Thus, the high temperature heating may be applied incombination with the hot working operation. In this instance, the metalwill be subjected initially to a high temperature, for example, 2100 F.,2200 F., 2300 F., etc., and then worked rapidly, as for example, byextrusion, in order to finish the hot working operation while the alloyis still at a temperature above about 2000 F., e.g., about 2100 F. Inthis manner, the heat remaining from the hot working operation isutilized to effect the high temperature heating of the heat treatment.Such a combination of high temperature and hot working may be desirablewhen fine grain size is important in the application where the wroughtthermal member is to be used.

Alloys contemplated in accordance with the invention are highlyresistant to oxidation andprovide a highly desirable combination ofproperties in the temperature range of interest in the heat engine art.Stress rupture tests made on the nickel-chromium alloy provided by theinvention have demonstrated that the alloy has a rupture life of atleast about 50 or 150 hours or much longer when subjectedto a stress of30,000 p.s.i. at 1500 F. Thermal members made by hot and/or cold workingoperations of the heat treated alloy exhibit a high combination ofproperties, including strength, ductility and resistance to stress, tocreep, to rupture, to heat, to corrosion, to erosion, to oxidation, topitting and to other destructive influences of other variousoperatingmedia at elevated temperatures.

High cobalt alloys comprise about 12% to 18% chromium, about 20% to,

40% cobalt, about 1% to molybdenum, with an aluminum plus titaniumcontent of about 4.8% to 8.5% and with the ratio of aluminum to titaniumbeing within the range of about 05:1 and about 3:1, preferably about08:1 and 1.6:1, about 0.05% to about 0.35% carbon, up to about 5% iron,and the balance essentially nickel. More preferred high cobalt alloyscomprise about 14% to about 17% chromium, about 23% to 35% cobalt,

especially about 23% to about 30% cobalt," about 2% to.4% molybdenum,ab,out,,5.% to 7 %,.Q .,al,t1minum plus titanium with the ratio .of

aluminum to titanium being between about 0.8:1 and 1.611, about 0.10% toabout 0.25% carbon and the balance essentially nickel.

The afored'escribed high cobalt alloys preferably contain small amountsof boron and zirconium in order to provide optimum strength at elevatedtemperatures.

When employed in the wrought condition, the alloys contain about 0.0002%to 0.009% boron and about 0.01% to about 0.25% zirconium. Preferably,the alloys will contain about 0.0004% to 0.007% boron and 0.01% to 0.15%zirconium or, more preferably, about 0.0005% to 0.005% boron and about0.03% to about 0.08% zirconium. It is to be understood that theaforedescribed preferred high cobalt alloys are malleable and can beproduced in the form of wrought thermalmembers in the absence of boronor zirconium. When it is desired to produce the preferred high cobaltalloys in the form of castings, the boron content can be increased to avalue as high as 0.02% and the carbon content may be within the range ofabout 0.05% to about 0.5%. Those skilled in the art are aware that, ingeneraLcast articles made of high temperature alloys possess superiorhigh temperature strength properties as compared to wrought articlesof'the same or substantially the same composition. However, a practicaldrawback existing with the production of the castings is the lack ofuniformity which has beenfound to characterize finished parts made ofcast alloys even when the castings ar made from the same heat of metal.

In order to provide improved strength in service at elevatedtemperatures, wrought thermal members made from the preferred highcobalt alloys described hereinbefore are subjected to a heat treatmentbefore use at elevated temperature service. The heat treatment maycomprise a double heating including a high heating at about 2000 F. toabout 2400 F. for at least about hour up to about 4 hours, e.g., about 1hour, followed by a reheating at a lower temperature of about 1500 F. toabout 1800 F. for at least about A hour to about 48 hours, e.g., about 4hours to about 24 hours. It has been found that certain alloys developoptimum properties after a triple heating in which each successiveheating -is conducted at a lower temperature. Such a heat treatmentcomprises a high heating under the same conditions as for thedoubleheating treatment and preferably about 2150 F. to about 2300 F. forabout /1'120 about 4 hours, followed by a reheating at about 1700" F. toabout 2100 F. for about /2 to 8 hours, e.g., about one hour, and areheating at about 1500 F. to about 1800 P. such as that described forthe double heating treatment. furnace cooling of about F. after thefir'stheating operation may be employed if desired. A feature of thevery high strength alloys containing the aforementioned special amountsof cobalt is that these alloys cannot be softened to any substantialextent by heating to a'high temperature followed by a rapid cooling. Thepreferred high cobalt alloys provide a high combination of properties atall temperatures of interest in the heat engine art. These alloys whensuitably heat treated have good notch strength and resist the undesiredgermination of grains which sometimes occurs in other alloys subjectedto critical straining at elevated temperatures.

The heat treated preferred high cobalt alloys described hereinbeforeprovide outstanding properties and an outstanding service life whenemployed in the found highly stressed thermal members. at hightemperatures,

and then extruded and hot rolled rods. The 1 about 222S F. for

given a heat treat- Heat dance with jected to the. rupture test TABLE IIsolidification, the ingot was heated rolled to five-eighths inchdiameter ingot was heated to a temperature the extrusion and hot rollingoperations. Samples were cut from the hot rolled rods and then mentbefore beingsub treatments which have been employed in accor the presentinventionare set forth in the following table 2' to 35% will have arupture life of hen tested at 1600 F. under i. Heat treated alloys willife of at least about 600 hours, and often at least about 1000 hours oreven 1500 hours or more,

ition to a rupf about 30,000 p.s.i. at 1500 F. igh cobalt alloy is foundto develop high jected, in the form of Wrought turbine blades, to a heattreatnly the lower temperature reheating cted in the heat treated cond 7range of about 23% at least about 200 hours w a st ress of about have arupture 1 when subje ture test at a stress 0 The preferred h rupturestrength when s thermal members, e.g., ment comp .1 tfd S S00679933612400738170037 09906 291 C C 0 0 0 0. m 0 a e Mm mmWWWwW.M%QMMM%B%M%M%%H%%MM%%U%W$%%% r r. 0 G QO MQGG C A A W QG e mmm M gA ha A11 Lim w th m m an m as h qs s mjffi m Jsss m m mssqi s L r SS rhs sl rrrh h h rrSsr t d m mm a na a na mm 3m 1 ea 7 11 41 11 44 1 421 11 I. 12 1 T. C i t T... C Ah m i a. 2 .F a. a. a. :3. I. f in a s m mGABBSCFEFSIIJIJCLMNUYWNOPLLA .L FFF FFF FF FFFF FFFFF F F FFFFF t m e .5D T ooufiooo oooono Ooouoo o0o0ooooo ua m mmm mnm mmhwmm m mmw m h mmmmd e em 0 I I I I 000 5fl5 59 5 03 5m660 0 0 m5305 r W I 0 5.. n LLQ 1 11 1 y 1 1 1 1 1 2 2 2 LLLLL s 0 l 2 I I I I I n c m m d a a 5 C O H n ma T H a M u u u u U n n C e .1 m 8 I n n n U "R C M m .h E N a .0 n P an I II A l de 0 l 1 A i a E I 6 M i n n v t t m B 1 m mu m m amt h s III hh h l t e a t. a that i a a m m I :2. m .F m em m m y I III FFF FFFFF F edufl m m I "I: 0 d u coo con 0 0 00000 B th 0 M. ufluu m @0050. u Wmse c I III 333 33 3 3 2 0 S t 22 2% 22222 m n mm I flw a m t S T n u un n II I 03 s st 1 I III 1 m m w m I umo ut I III rm W T C C o ."I" I aI I II Mm au m "III I m Mn m I IIIII F O u one on 1 X rmm rLaaataazaawnmmnmmwwwmahwammhuhaah 0 5 0 5 0 5 0 5 0 2 3 4 4 5 5 0 6 7 eLLLLLLLLLLLLLLLLLLLLLlllLlLlllLLlLl dfidn m d O 6 e t 5 t n C .tlaa383a303BBaaaaaaaflaaaaflaflaaflz aafia n t muuevamn em m amBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBR .m. m m n i inm r 1 n u o e r r a wn is a ay Xaabag mmm m ma .1 v .8 l n 0 e a a 1 t. no.5a 1 1 t e a a S 6MW. 12270 12619131050220012101016022201 mnmm m h 1 0 W d m muh .1 A a 6m l e 111 11110101.111 1 1101111111 1100]111.1 3A00 u k g O h n .T- n td m t t e e w 0 0 .0 o0 0 O 0 0 0 0 0 0 0 0 n 0u00 0 uo000000000000 n mm nw t a mm e m m n t H C oflu e m n n h n N m m. a .1 f n u t m d S t Oe hmmu hhwhm omwwh nwwhmnhh ha whmh w mu .4 m m mmdbn mm m m mew y R 00.00 .00 .000 .0 .00 .0 Mme m YZ O 8 h t 0.1.1.1 6 C 11 00000000000000000 .0000000000N0000000 0 C Au 8 .1 e n n n 011 mw r e m fim cefl m a ttw s t C i on E 3X 3 H c t a a pawmmwhhmwmhmhwmmwmyhanwhuman. when m n o m m n 7 0 t w a t .1 1m 1% n HT 2 2215222222322232223222222223222222 mmm m. m wm m m m o u z d 0 w w.1 ha a r. t 1 8d 6 n t. I t. I d .1 n n t O C 0h 6 6 d8747571.00430004599127912934777552559 MMHQ m o a C H.S Ub v. H T. t a ff n S e E 887977 9147807709398078093831002. 089 m 2L e a a 0 3 a t y W tm e .m m m mA 22 22a2232222223122azaleas 32232233322 mw 0 m cm W i wfm mP n M td wfi m fhs e fi e n m A 847 616430910322339443 154324029 .m m we m n m W Cm w w I m m 0 P T m 009 00900160091109.1158649 001006097 ml 0e m C a.m 0. 3 Oh U n H I 5 un mm m m h wm R ew w e e b 6 h a a e O .1 1V. d a l r 0 t f a a m 46853420038 7057657306 255063033815 mm T WM 0 g ee.w m n .d H W a d m o .1 m1 n assas .ass J i aan n rnvm e n wu c o m eo e t 1 m e a PWC 888988988012700008 0RWOUQWSRFQQQWQWSQQQQQA OZO 1 5 .mn a W C e U W I h 6 u 6 0.0 m gt 2 222222 232222222332222222232223230.mw m u S. C m y unou t Wh 0 m n 8V. .8 r. t e 5h n M mu a 2132946705580117.1202242609952873701 Nm hm m CH kT m 010. e S O t W e H mm Wvwmw 98877098918900006072992138552727894 V.1 um m 8 m e V d mot mu d H mmt a t 0C d hm c Pm m n wmwnnwmnmmmunmmwru mmmmwm t mm .w a m an w am e.1 o d whn ew a my wwdefl fl em w m m I III rmm mm m r am nnmmm n. t IIIr mom v m d s dae an m w I III m awmm nfla mm u e meflh s Wv n I IIINrmed pN .Ibmb e .m ddd n 0 cm A 012345 O d O eo h .mdDnSeV d t. 1333333 beta 0 cfcbtofilmsaaaafarm bath was then poured into a cast ironmold. After TABLE IV' [Test Conditions-l600 F. and 30,000 p.s.L]

Alloy No. Heat 'lreat- Rupture ment Life, Hours A 135 A 137 A 125 A 96'In order to demonstrate the. high order of stress rupture propertiesdeveloped by the preferred cobalt-containing alloys contemplated inaccordancewith the invention at temperatures of 1500 F., 1600 F., 1700"-F., and 1800" F., the following table sets forth the results of stressrupture tests conducted upon Alloy-18 at these temperatures. The testspecimens were prepared from hot rolled bar stock and were subjected toa heat treatment comprising heating to about 2275 F., furnace cooling100 F., air cooling, heating to about 2000 F. for about 1 hour, aircooling, heating to about 1600 F. for about 4 hours and air cooling.

TABLE V Stress Rupture Test Conditions Life, Hrs. Elongation,

Percent Temp, F. Stress, p.s.l.

62 as 40, 0 1 L500 so. 000 1, 085 10 25, 000 1, 587 5 40. 008 6g 30. 00L600 25. 000 280 15 20,000 748 14 25, 000 8 22 20, 000 38 30 1,700 15.000 113 13. 5 l 12, 000 184 7, 5 8. 000 1, 048 2. 5 10, 000 l1 1,800 S,000 36. 5 52 5' A further series of stress rupture tests were conductedupon hot rolled bar stock from Alloy 18 whichhad been heat treated at2150" F. for 2 hours, air cooled, and then heated 1600 F. for about 4hours. This heat treatment is designed to provide a finer grain sizewith high properties. The data are presented in the following table:

A series of stress rupture'tests was conducted upon-Al loy 35 todemonstrate the effects of heat treatment upon the rupture life of thealloy at 1600 F. and 28,000 p.s.i. The heat treatments and theaccompanying rupture lives 5 under the foregoing conditions are given inthe following Table VII:

TABLE VII High Heating Temperature, Reheatiug Rupture Elongation,"F.(2-hourtreatrnent),A.C. Conditions, Life, Hours Percent F./hrs.

It was observed that the alloys sub ected to the foregoing tests werealso hlghly resistant to creep, another factor which is very importantin evaluating metals for use in thermal members which are subjected tohigh temperatures and high stresses in service. In addition, the heattreated wrought alloys are characterized by-a high strength and adequateductility at ordinary temperatures as evidenced by a yield strength ofat least about 100,000

p.s.i., a tensile strength of at least about 160,000 p.s.i. and anelongation of at least about 20% in 2 inches when measured atatmospheric temperatures.

As previously noted, preferred cobalt-containing cast 5 alloys withinthe present invention provide high properties at elevated temperatures.The compositions of satisfactory cast alloys are given in the followingtable:

TABLE VIII 'Per- Per- Per- Per- Per- Per- Per- Alloy No. cent cent centcent cent cent cent Cr Co Mo Al Ti 0' Ni 28. 7 3.20 3 26 2. 22 0.15 Bal.28.0 3.28 3 78 2. .53 0.18 E21. 28 3. 40 4. 36 2. 83 0. l8 Bal. 28 1.208, 22 2.02 0. 13 B211.

1 Including small amounts of boron and zirc anium resulting from theadditions of about 0.003 2; and about 0.05% of these elements,respectively.

The properties of the foregoing cast alloys tested in the as-castcondition and at 1600 F. and 30,000 p.s.i. ar e as follows:

timum strength at elevated temperatures.

1 T.S., p.s.i.=Tensile Strength in pounds per square inch. 2 EL,Percent=Elongation in percent.

Low cobalt alloys It has also been discovered that certain alloys freeof columbium and tungsten and containing relatively low amounts ofcobalt comprehended in the scope of the present invention will providevery satisfactory heat and stress resisting thermal members and possesscommercial malleability. These alloys possess advantages in that thehighly strategic elements columbium and tungsten are unnecessary fortheir production and no cobalt or only small amounts of cobalt, which isitself a strategic element, are required. Such alloys comprise about0.05% to about 0.35% carbon, about 5% to 17% chromium, up to aboutcobalt, about 1% to 10% molybdenum,

about 3.5% to 8.5% of aluminum plus titanium with the ratio of aluminumto titanium being about 0L5z11up to about 3:1. These alloys desirablycontain boron and zirconium in very small amounts in order to provideop- It is to be understood that these alloys likewise are malleable inthe absence of either or both of boron and zirconium. When boron ispresent, it is employed in quantities of a few tenthousandths of one percent, e.g., about 0.0002% or 0.0003% up to about 0.009%, preferably0.000s% to 0.009%, e.g., 0.0007% to 0.007%.

Zirconium, when used, may be present in amounts of about 0.01% to about0.25%, e.g., about 0.03% to about 0.08%.

I Special wrought alloys having relatively low cobaltcontents includethose set forth in the following schedule:

Improved high temperature properties are developed in the foregoing lowcobalt alloys, including cobalt-free alloys, when boron and zirconiumare present in very small amounts Within the ranges set forthhereinbefore.

It is to be understood that the alloys of column A in the foregoingschedule are preferred inapplications where ductility at servicetemperatures intherange of about 1200 F. to about 1600" F. is of primeimportance, e.g., rotor wheels. When high strength at the servicetemperature range of about 500 F. to about 1800 F. is required, as inturbine blades, then the alloys defined in column B of the foregoingschedule are desirable.

For optimum strength, including high rupture life at the servicetemperature range of about 1500 F. to about 1800 F., the alloys ofcolumn C in the foregoing schedule are preferred. When high notchstrength at service temperatures in the range of about 1200 F. to about1500 F. is of prime importance, the alloys of column D in the foregoingschedule are preferred.

' amazes The copresence of molybdenum, boron, carbon and zirconium incombination with chromium, aluminum and -titanium in thespecialproportions indicated hereinbefore for the special low-cobalt alloyscontemplated in accordance with the present invention enables theproduction i of wrought nickel alloys having high rupture life of thesame or higher order than other wrought alloys containf ing thestrategic elements columbium and tungsten and/or containing largeramounts of cobalt.

The presence of chromium in the aforementioned ranges is important andthe presence of chromium in combination with the other elements impartsoxidation resistance to the alloy and is also important as a matrixstiffening or hardening element. Aluminum and titanium are importantharden- .ing and stiffeningelements. Aluminum is also advantageous inimparting oxidation resistance to the alloy. Carbon is important incombination with the other ingredients of the low cobalt compositions assetforth hereinbefore. Carbon preferably is present in amounts of about0.08% to about 0.18% in order to assist in maintaining fine grain sizeand to impart improved rupture strength at elevated temperatures. Thepresence of molybdenum in the alloy is particularly effective incombination with the amounts of the other elements of the low cobaltcompositions set forth hereinbefore', especially in enabling theproduction of alloys having good high temperature properties and themolybdenum preferably is present in amounts of about 2% to about 4%.Iron is an optional element and may be present in amounts up to about5%.

Molybdenum, like chromium, has a matrix stiffening or hardening effecton all the alloys described here in and is about twice as effective aschromium as a matrix hardener. In the special low-cobalt alloys definedin columns B and C of Table X, it is more pre- 'ferred when the aluminumplus titanium content is at a high combination of properties at elevatedtemperatures.

It is also to be understood that the low cobalt alloys definedhereinbefore are malleable and may be worked into thermal members suchas blades for aircraft turbojet engines andthe like. The alloys may alsobe fabricated as castings for use as thermal members. In cases where itis desired to employ the alloy in the form of cast thermal members, theboron content may be increased to as high as about 0.02% and the carboncontent may be increased to as high as about 0.5%. As notedhereinbefore, it is generally thought that cast thermal members are notas consistent in properties from piece to 'piece as is the case when thethermal members are worked to shape as by forging, hot rolling,extrusion, etc.

It is to be understood that the aforementioned wrought low cobalt alloysdevelop their best properties at high temperatures when subjected to aheat treatment such as the double heating treatment or the tripleheating treatment described hereinbefore for the wrought high cobaltalloys. Like the cobalt-containing alloys described hereinbefore, thepreferred low cobalt alloys comprehended in accordance with the presentinvention are characterized by the fact that they cannot be sub- ..ispresented:

about 20 hours at about 1300 F.

TABLE XI Per- Per- Per- Per- Per- Per- Per- Per- Per- Alloy No. contcent cent cent cent cent cent cent cent Cr Fe Al Ti 'Mo 0 Zr N U 10. 590. 23 2. 93 1. 84 3. '11 0. 06 0. 072 Ba]. 11 58 0. 32 2. 51 2. 62 2. 360. 06 0. 053 B111. 10. 77 0. l3 2. 73 1. 80 3. 06 0. 06 0. 057 Bal.10.85 3 64 2. 84 1.83 2. 94 0. 05 0.056 Ba]. 10. 62 3. 95 2. 73 1. 65 2.95 0. 06 0.061 B211. 10. 25 0. 2. 91 2. 51 2. 95 0.07 0. 057 Bal. 10.92 1. 53 3-0 3.0 3. 03 0.08 0.041 'Bal. 8. 16 1. 83 3. 8 2. 7 3. 12 0.0S 0. 041 Bal. 10.33 0.18 3. 43 2. 40 3 03 0. 08 0.018 Bal. 8. 31 0. 183. 63 2. 67 3. 00.. 0. 09, 0. 055 Bai. 7. 91 0. 40 3. 64 2. 70 3. 92 n.00 0.062 Bal. 7.80 0. 14 3. 32 2. 46 4. 86 0. l0 0. 050 Bal. 10. 16 4.76 0. 18 3. 13 2. 22 3. 03 0. 08: 0. 053 Hal. 9. 51 4. 73 0. 3. 60 2. 663. 02 0. 00 0. 062 Bal. 8. -6 5. 04 0. 16 3 56 2. d7 3. 04 0. 10 0.05232.1. 14. 73 4. 78 0. 17 2. 83 1. 77 3. 02 0.08 0.052 Bal. 10.16 0. 162. 3. 20 2. 86 0. 06 0.051 Bal. 11. 09 8. 10 0. 16 3.0 2. 5 3. 07 0.080. 048. Bal. 8. 4-1 4. 83 0. 20 3. 59 2. 67 2. 93 0.08 0.057 Ba]. 11. 568. 16 0. l6 8. 3 2.0 3.05 0. 07 O. 041 Bal. 11. 13 7. 73 0. 19 3. 0 2. 42. 96 0.09 0. 046 Ba]. 8. 30 4. 84 0.30 3.71 2. 74 3. 01 0. 09 0.055Bal. 11.87 0.15 2. 86 2. 53 2. 95 0. l0 0 041 Bal. 8.11 5. 43 1.03 3. 82. 7 2. 89 0.09 0 041 Bal. 10.39 0. 19 3. 16 2. 26 2. 95 0. 07 0. 052Be]. 9. 75 1.01 0. 41 3. 46 2. 57 2. 85 0. 09' 0. 053 Bal. 11. 86 4. 940. 16 3.02 2. 3.03 0. 08' 0. 046 B21. 14. 27 4. 96 0. 30 3. 16 2. 253.03 0.08 0. 041 Bal.

Norm-Alloys to 44 contained about 0.002%, 0.007%, 0.007%, 0.007%, and0.003% boron. respectively. Alloys to 52, 55 to 59, 61 to 6 66 and 67contained boron resulting from an addition of about 0.003% boronto therespective melts and Alloys 53, 54. 60 and 65 contained boron resultingfrom an addition of about 0.005% boron to the respective melts.

1 Balance includes small amounts oi manganese, magnesium, silicon,coppenetc.

The rupture life of heat treated alloys 40 through 44 TABLE XIV at 1500F. and a load of 30,000 p'.'s.i. is given in the [Test Conditions-1350"F. and 70.000 p.s.i.]

Heated for about 4 hours at about 2100 F., air cooled, and heated heatedat lfiooo [or about 4 hours about 20 hours at about 1300 F., air cooled.I V 2 Heated for about 8 hours at about 1975 F., air cooled, and heated7 TABLE xv [Test Conditions-1800" F. and 8,000 p.s.i.]

following table: I g

' TABLE XII Alloy N Heat Treat Rupture Life, Elongation,

rnent, F. hours percent Alloy N0. Rupture Life, Rupture Life, 40 45 i 257 7 5 1 Alloys heated 2 hours at temperature noted, air cooled, andthen r The rupture lives of other alloys after the indicated-- heattreatments and under the indicatedconditions are" ,Almy g g f gf g shownin the following tables:

L 103 TABLE XIII 50: B-. iii [Test Conditions-1600? F. and 25,000p.s.i.] ii 5s 2,325 10s Alloy N o. Heat Treat- Rupture Life, 7 67 142ment hours H 1 Alloys heat treated 2 hours at the indicated temperature,air cooled 45- .L '5 and then heated for about 4 hours at 1600 F. 46 X.163 g g: In manufacturing the foregoing alloys, nickel and .49. L--.240 chromium were melted in an induction furnace and the 29- -3molybdenumwas then incorporated in the melt. Carbon was then addedin'the form of a master alloy contain- 379 ing about 10% carbon and 90%chromium. Thereafter, 2? 1 8 about one-half of the aluminum was added,followed by an addition of magnesium and zirconium. The balance g of thealuminum was added next, followed by the intrm duction of the titaniumand finally the boron. Usually, the zirconium and boron, and sometimesthe magnesium 'j V239 and titanium, are'added as master alloys. Withrespect 66. CW 172 totitanium, it. is preferred to add the titanium inthe purest elemental, form available. The molten bath was then pouredinto a cast iron mold. After solidification, the ingot was heated andthen forged and rolled to fiveeighths inch diameter hot rolled rods. Theingot was heated to a temperature of about 2225 F. for theforging andhot rolling operations.

Low chromium, high cobalt alloys It has been found in applicationsinvolving exposure of wrought thermal members to very high servicetemperatures on the order of about 1700 F. or higher, and involving therequirement for a high order of commercial forgeability, that specialalloys within the inven-.

'16 scribed low chromium, high cobalt alloys preferably are subjected toa heattreatment before being employed in service. Either the doubleheating treatment or the triple heating treatment described hereinbeforein conjunction 'with other high cobalt alloys within the scope of theinvention may be employed in treating the low chromium, high cobaltalloys. These alloys in the heat treated condition will have a rupturelife of at least about 100 hours, and usually about 200 hours or more,when tested at about 1600 F. and 25,000 psi. The following tablecontains the analyses of satisfactory low chromium, high cobalt alloysproduced in accordance with the invention:

TABLE A Alloy No.

Per Percent Percent Per Per- Percent cent Percent Per- Percent cent CrCo Mo Al Ti Zr B l Ni 1 Amounts added to melt. Balance includes smallamounts of manganese, magnesium, iron, silicon, copper, etc.

tion are particularly suitable. These alloys contain about 7% to 9% or11% chromium, at least about 8%, e.'g., about up to about 30%, cobalt,about 5% to 8.5%

of aluminum plus titanium with the ratio of aluminum to titanium beingwithin the range of about 0.5 to l and about 3 to 1, about 1% to 10%molybdenum, up to about 1 5% iron, and the balance essentially nickel.Preferably,

such alloys contain about 2% to 6% molybdenum and having a ratio ofaluminum to titanium which is between about 0.8 to 1 and about 1.6 to 1.

In order to provide optimum strength at service temperatures of about1700 F. or higher, it is preferable that these alloys contain smallamounts of boron and zirconium within the range of about 0.0002% to0.009% boron and about 0.01% to about 0.25% zirconium. Preferably, thealloys'will contain about 0.0004% to Machined rupture test specimens cutfrom hot rolled rods made from the foregoing alloys were heat treatedand subjected to stress rupture tests at 1600 F. and 25,000 p.s.i. Theresults of the stress rupture tests are) presented in the followingtable:

TABLE B Alloy N 0. Heat Treat- Rupture mcnt Life, hours Q 205 A 251 B201 Alloy No. 70, when given Heat Treatment B and subjected to a stressrupture test at 1800 F. and 8,000

0.007% boron and .01% to 0.15% z1rcon1um or, more 4 p.s.1., exhtbrted arupture life of 141 hours. preferably, about 0.0005% to 0.005% boron andabout The following table sets forth the compositions of 0.03% to about0.08% z1rc0n1um. other alloys contemplated 1n accordance w1th thepresent Wrought thermal members made from the'aforedeinvention:

3 TABLE XVI Pl.-1- Per- Por- Pvr- Por- Pcr- Per- 4 Per- Per- Per- AlloyN 0. cent PPM. cent cent cent cent cent cent cent cent Cr Co Fe Al Ti M00 Zr N l l 0. 34 2 3s 1. 55 3.15 0. 0s 0. 040 0.00 B01. 002 233 1.532.31 0.07 0. 0 5 00 15 33.1. 0 21 2.23 1 02 3v 17 0. 07 0. 005 0005 B31.

70 2.34 1.0 3 01 0. 00 0.053 001-15 1331 3.73 2. 30 1 2. 33 0. 05 0.0530.001 Bal 0.10 2.35 1 51 1.10 0. 07 0. 000 0 003 1741 0.15 2. 35 1 531.00 0 00 0.057 0003 B31 0.13 2.40 1 47 3. 00 0.01 0.053 0, 003 Del.0.10 2. 34 1 52 3.04 0 10 0.002 0 003 0 2. s4 1 15 2 00 0. 0s 0. 0340.003 B3]. 0.15 2 47 1 44 4.04 0 00 0. 05s 0 005 Bal 0.25 1.30 2 70 3.170.05 0 043 0.003 1301 4.75 2. 33 1 72 3. 04 0.03 0.053 0. 003 1331 0 222 1 00 3.04 0. 0s 0 072 0 003 Be] 0. 30 2. 30 1. 59 3. 12 0. 07 0 055 0003 1321 0. 21 2.09 1 00 2. s2 0. 7 0.072 0 003 B31 4 30 2. 42 1.51 3.03 0. 0e 0. 053 0 007 B01 3. 02 2. 20 1,50 2 03 0. 00 0. 0 .0 0 005 13313.70 2. 43 1 50 3.31 0. 07 0. 04 0 003 B31 3. 71 2.10 1 4 71 0.00 0. 0450 007 Bal 0.12 2.00 1. 32 2. 04 0.00 0. 05s 0 003 E01 0.13 3.41 2.00 3.03 0. 00 0. 055 0 005 1351 0. 23 2. 73 1. 3t 7. 3r 0. 00 0 105 0 00: B0110. 40 0.35 2.39 1.51 2. 35 0.11 0.030 0 003 B01 19.42 0.17 2.37 1. 3 030. 0s 0. 055 0 003 B21 10 00 0.30 2. 34 1.54 3.07 0.11 0.002 0 003 R11118.32 0.30 2.33 1. is 2.38 0.10 0. )5 0 0021 B31 12. 00 0.22 1.32 2.533.34 0.05 0. 57 0 005 Be! 773 0.31 2.53 1. 00 3.02 0. 0." 0. 052 0 003E01 7.20 0.77 2. 73 1.01 2 s9 0 5 0 05 0 002 1321 3.00 3. 00 2.33 1.00 310 0.07 0. 053 0 003 1011 10. 00 0. 20 2.53 1 3.04 0 07 0 .0 0 005 130110. 21 0.11 2. s5 0. 00 3.09 0. 07 0 2 0,004 133.1 9.74 0. 21 2.57 2. 053.15 0.07 0 052 0.003 1431 0.14 .233 1. 45 1.10 0.07 0.002 0.003 Hal 030 2. 20. 1. 50 2 02 0.10 0. 053 0.003 B31 0. 44 2.35 1.70 2. 05 0.11 0.053 0. 003 E01. 1.14 1.17 2 57 3.01 0.04 0.052 0.003 1321.

Balance includes small amounts of manganese. magnesium, silicon, copper,etc.

The rupture lives of the foregoing alloys, as determined at 1500 F. and'30,000 p.s.i; after a heat treatment as noted, are given in thefollowing table:

TABLE XVII RupturcLiie, Hours Alloy No.

Heat Treat- Heat Treatment No. 1 ment No. 2

1. Heated for about 4 hours at about 2100 F., air cooled, and heated [orabout 2) hours at about 1300 F., air cooled.

2. Heaiel for about 8 hours at about 1975 F., air cooled, and heatedabout 20 hours at about 1300 F.

TABLE XVIII Per- Per,-. Per- Per- Per- Pcr- Per- Per- Alloy No. centcent cent cent cent cent cent cent Co Mo r Al Ti B Zr Specimens madefrom the foregoing alloys were heat treated and subjected to stressrupture tests at 1700 F. and 20,000 p.s.i., with the following results:

TABLE XIX Rupture Life, Hours Heat Treating Temperature, F. Alloy AlloyAlloy Alloy Alloy Alloy 109 110 111 112 113 114 o 1 Specimens held forabout 2 hours at temperature noted, air cooled and reheated at about1600 F. for about 24 hours.

Two other series of'tes'ts were conducted'to illustrate the effects ofthe zirconium-boron treatment upon the rupture life' of forged androlled alloys with the following results:

. TABLE XX Per- Per- Per- Per- Per- Per- Per- Per- Rup- Alloy N 0. centcent cent cent cent cent cent cent ture 00 Mo Or Al Ti 0 B Zr Life,

Hrs.

30 3 15 3. 0 2. 3 0. 10 n.a n.a. 100. 5 30 3 15 3.0 2. 3 0.10 n.a. 20530 3 15 3. 0 2. 3 0. 10 367 30 3 15 3. 0 2. 8 0. 10 no. 301 30 3 15 3. 02. 8 0. 10 626 1 Contains boron resulting from addition of 0.003% and/orcontains zirconium resultin g from addition 010.05%.

2 Test conditions: 1600 F. and 25,000 p.s.i. stress. n.a.=none added. I

The foregoing alloys were subjected to heat treatments as 5 follows:

TABLE XXI Alloy N o. Initial Heating Reheating 2,325 Fig-2 hrs.,A. C2,325" F.-1 hr.-, A.C

It is to be noted from the foregoing tabulation that the incorporationof special amounts of either, and particularly both, of the elementsboron and zirconium in alloys contemplated by the present inventioncontributes to the high temperature strength properties achievedtherein.

Alloys produced in accordance with the invention are resistant togermination or abnormal grain growth when subjected to elevatedtemperatures after straining. The alloys are also highly resistant tooxidation, a desirable characteristic in gas turbine blade applications.The alloys are also adaptable to production in wrought form such asbars, rods, billets and the like, starting with a big ingot casting.Many prior alloys have not been susceptible to mill processing startingwith a big ingot and this lack has been undesirable from a number ofstandpoints, including higher cost of other processing methods, lack ofuniformity in properties and structures from piece to piece, etc.

A preferred method for the mill processing of alloys contemplated inaccordance with the invention comprises preparing a melt of theparticular alloy in an induction furnace which may or may not beprovided with a vacuum or other special atmosphere, casting the alloyinto ingots'approximately 9 inches in diameter and about 28 inches long,heating the ingots to a temperature in the range of about 2000" F. toabout 2100 F., extruding the ingots with a glass lubricant to providebillets having a cross section of about 4 square inches to about 9square inches, and thereafter hot rolling the billets thus prepared. Itis preferred that the subsequent hot working, e.g., hot rolling, beaccomplished within the temperature range of about 1900 F. to about 2225F.

It has been found that the present nickel-chromium alloys possess bothhot workability and cold workability and can be produced on anindustrial scale into products acceptable to the trade. For instance,when nickelchromium alloys, such as are illustrated hereinbefore, aremade it has been found that they can be fabricated in modern machinery,such as by modern high-powered forging, rolling, drawing, upsetting,extrusion, machining, grinding, etc. The alloys of the present inventioncan also be employed in the cast form, e.g., as precision castings.

The present invention provides a special nickel-chromium alloy which isparticularly applicable to the manufacture of and use as thermalmembers. The term thermal members as employed herein is intended toinclude structural members which in use are subjected to heat and stressat elevated temperatures, particularly such structural members of heatengines, such as jet engines, gas turbines, turbo-superchargers,exhaust-gas power recovery turbines, etc., by which heat is transformedinto mechanical work. Illustrative examples of some of the thermalmembers contemplated by the invention include turbine blades such asrotor blades or buckets and stator blades or nozzle guide vanes, rotorwheels, structural rings for gas turbine assembly, etc.; valves, valveseats and accessories, exhaust manifolds and supports therefor, etc.;combustion liners or flame tubes, tail cones, after-burner parts,vaporizer tubes and other high temperature tubular members, hightemperature gas seals, etc.; high temperature springs and otherresilient members; high temperature bolts, studs, fasteners, nuts, etc.;

high temperature stiffening and supporting members; etc.

The present applicationris a continuation-in-part of my co-pendingapplications Serial No. 250,161 and Serial No. 250,162, both filedOctober 6, 1951 and both now abandoned.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the artwill readily,un-

derstand. Such modifications and variations are considered to be withinthe purview and scope of the inven tion and appended claims.

I claim:

1. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for' extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 14%- to 17% chromium, about 2% to 4% molybdenum, about 23% to 35%cobalt, about 0.1 to 0.25% carbon, about 5% to 7% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 0.8 to 1 up to about 1.6 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.15%zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by'a rupture life of atleast about 200 hours at 1600 F. and 25,000 pounds per'square inch.

2. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 12% to 18% chromium, about 1% to 10% molybdenum, about 20% to 40%cobalt, about 0.05 to 0.35% carbon, about 4.8% to 8.5% of aluminum plustitanium with the ratio of aluminum to-titanium being in the range ofabout 0.5 to 1 up to about 3 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.25zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by a rupture life of atleast about 200 hours at 1600 F. and 25,000 pounds per square inch.

3. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods .of timeunder conditions of high stress and elevated temperature which comprisesabout 5% to 20% chromium, about 1% to 10% molybdenum, about from about0.01% to about 0.25% zirconium, and with the balance essentially nickel,said alloy being ch-arac-- terized in the heat treated condition by arupture life of at least about hours when tested at 1600 F. and

25,000 pounds per square inch.

4. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 5% to 9% chromium, about 1% to 10% molybdenum, not more than about10% cobalt, about 0.05 to 0.35% carbon, about 5.5% to 8.5% of aluminumplus titanium with the ratio of aluminum to titanium being in the rangeof about 0.5 to 1 up to about 3 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy beingcharacterized by a high level of rupture strength in the temperaturerange of 1700 to 1800 F.

5. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 7% to 11% chromium, about 2% to 4% molybednum, up to about 8%cobalt, about 0.05% to 0.25% carbon, about 5.5% to 7% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 3 to 2 up to about 1 to 1, not more than about 5% iron, from about0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy beingreadily wrought and ei ng characterized by a high combinationofproperties atelevated temperature.

A hot-workable, coldworkable, heat-resistant ,alloy particularly adaptedto service as a thermal member for extended periods of time underconditions of high stress :and elevated temperature which comprisesabout 10% to 15% chromium, about 2% to 4% molybdenum, about 3% to 8%cobalt, about 0.05 to 0.25% carbon, about 4.5 to 6% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 3 to 2 up to about 1 to 1, not morethan about iron, from about0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy having ahigh notch strength at service temperatures of 'abouti120 0 to l500 7. Ahot-workable, cold-workable, heat-resistant alloy particularly adaptedto service as a thermal member for extended periods of time underconditions of high stress and elevated temperaturewhich comprises about7% to 13% chromium, about 2% to 4% molybdenum, about 3% to 8% cobalt,about 0.05% to 0.25% carbon, about 5% to 7% of aluminum plus titaniumwith the ratio of aluminum to titanium being in the range of about 3 to2 up to about 1 to 1, not more than about 5% iron from about 0.0002% toabout 0.009% boron, from about 0.01% to about 0.15% zirconium, andwiththe balance essentially nickel, said alloy having a high rupturelife in the service temperature range of about 1500 to 1800" F. p 8. Ahot-workable, cold-workable, heat-resistant alloy particularly adaptedto service as a thermal member for extended periods of time underconditions of high stress and elevated temperature which comprises about7% to 13% chromium, about 2% to 4% molybdenum, up to about 3% cobalt,about 0.05 to 0.25 carbon, about 5% to 7% of aluminum plus titanium withthe ratio of aluminum to titanium being in the range of about 3 to 2 upto about 1 to 1, not more than about 5% iron, from about 0.0002% toabout 0.009% boron, from about 0.01% to about 0.15 zirconium, and withthe balance essentially nickel, said alloy having a high strength atservice temperatures of about 1500 to 1800 F.

9. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 8% to 13% chromium, about 2% to 4% molybdenum, up to about 3%cobalt, about 0.05% to 0.25 carbon, about 4.5% to 6% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 3 to 2 up to about 1 to 1, not more than about 5% iron, from about0.0002% to about 0.009% boron, from about 0.01% to about 0.15%zirconium, and with the balance essentially nickel, said alloy havinghigh ductility at service temperatures of about 1200 to 1600 F.

10. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 5% to 17% chromium, about 1% to 10% molybdenum, up to about 10%cobalt, about 0.05 to 0.35% carbon, about 4.5% to 8.5% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 0.51 to 1 up to about 3 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by a rupture life of atleast about 100 hours when tested at 1600 F. and 25,000 pounds persquare inch.

11. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 7% to 11% chromium, about 2% to 6% molybdenum, about 10% to 30%cobalt, about 0.05% to 0.35% carbon,

- -22 abqntfi /t t 7 5% ofa u n a tn luetitaa m w th the ratio ofaluminum to titanium being the range of about 0.8 to 1 up to about1.6.t0 1, .not more than about 5% iron, from about 0.0002% to about0.009% boron, from about 0.01% to about 0.25% zirconium, and with thebalance essentially nickel, said alloy being characterized in the heattreated condition by a rupture life of at least about 100 hours whentested at 1600 F. and 25,000 pounds per square inch. I I Y 12.hot-workable, cold yvorkable, heat-resistant a1- loy particularlyadapted to service as a thermal member for extended periods. of timeunder conditions of high e s nd..,1evat.d temp ra which comp about 7% toI1 chromium,.about 1% to 10% molybdenum,

at least abput. 8% and .upto about cobalt, about 0.05% to 0.35% carbon,about 5% to 8.5 of aluminum plus titanium with the ratio, oi aluminum totitanium being in. therange of about 0.5 to 1 .up to about 3 to 1, not eth a out 5% r rfrem P t -0 to about 0.009% boron, from about 0.01% toabout 0.25 zirconium, andwith the balance essentially nickel, said alloybeing charaeterized in the heat treated condition by a rupture life ofat least about 100 hours when tested at 1600 F. and 25,000 pounds persquare inch.

'13. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as. a thermal member for extended periods of timeunder conditions of high stress -and elevated temperature whichcomprises about 5% to 20% chromium, about 1% to 10% molybdenum, up toabout 40% cobalt, about 0.05% to 0.35% carbon, about 4.5% to 6% ofaluminum plus titanium with the ratio of aluminum totitaniurn being inthe range of about 0.8 to 1 up to about 1.6 to 1, not more than about 5%iron, from about 0.0002%.to about 0.009% boron, from about 0.01% toabout 0.25 zirconium, and with the balance essentially nickel, saidalloy being characterized in the heat treated condition by a rupturelife of at least about hours when tested at 1600 F. and 25,000 poundsper square inch,

14. A hot-workable, cold-workable, heat-resistant alalloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40%cobalt, about 0.05% to 0.35% carbon, about 5% to 7% of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 0.8 to 1 up to about 1.6 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by a rupture life of atleast about 100 hours when tested at 1600 F. and 25,000 pounds persquare inch.

15. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted to service as a thermal member for extended periods of timeunder conditions of high stress and elevated temperature which comprisesabout 5% to 20% chromium, about 1% to 10% molybdenum, up to about 40%cobalt, about 0.05% to 0.35 carbon, about 4.5% to 8.5 of aluminum plustitanium with the ratio of aluminum to titanium being in the range ofabout 0.5 to 1 up to about 3 to 1, not more than about 5% iron, fromabout 0.0002% to about 0.009% boron, from about 0.01% to about 0.25%zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by a rupture life of atleast about 100 hours when tested at 1600 F. and 25,000 pounds persquare inch. V

16. A thermal member particularly adapted to service for extendedperiods of time under conditions of high stress and elevated temperaturewhich comprises about 5% to 20% chromium, about 1% to 10% molybdenum, upto about 40% cobalt, about 0.05 to 0.5% carbon, about 4.5% to 8.5% ofaluminum plus titanium with the ratio of aluminum to titanium being inthe range of about 0.5 to 1 up to about 3 to 1, not more than about 5%iron, from about 0.0002% to about 0.02% boron, from about 0.01% to about0.25 zirconium, and with the balance essentially nickel, said thermalmember being characterized in the heat treated condition by a rupturelife of at least about 100 hours when tested at 1600 F. and 25,000pounds per square inch.

17. The method for improving'the stress rupture properties of thermalmembers for service at high stress levels for extended periods of timewhich comprises establishing a molten bath of an alloy containing about5% to 20% chromium, about 1% to 10% molybdenum, up to about 40% cobalt,up to about.5% iron, about 4.5% to about 8.5% of aluminum plus .titaniumwith the ratio of aluminum to titanium being in the range of about 0.5to 1 up to aobut 3 to l and with the balance essentially nickel andintroducing into said bath shortly before casting boron and zirconium inamounts sutficient to provide respective contents thereof of about0.0002% to 0.009% and 0.01% to 0.25% in metal cast from the thus-treatedbath, casting metal from the thus-treated bath to ingot form and hotworking said ingot to provide wrought thermal membls characterized inthe heat treated condition by a rupture life of at least about 100 hourswhen tested at 1600 F. and 25,000 pounds per square inch.

18. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted for service for extended periods of time under conditions ofhigh stress and elevated temperature which comprises about 11% chromium,about 3% molybdenum, about 10% cobalt, about 0.7% carbon, about 2.6%aluminum, about 2.7% titanium, about 0.2% iron, about 0.003% boron, fromabout 0.01% to about 0.15% zirconium, and with the balance essentiallynickel, said alloy being characterized in the heat treated condition byhigh rupture strength at temperatures of about 1500 F. and higher.

19. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted for service for extended periods of time under conditions ofhigh stress and elevated temperature which comprises about 14% chromium,about 3% molybdenum, about 28% cobalt, about 0.11% carbon, about 2.9%aluminum, about 2.7% titanium, about 0.003% boron, about 0.04%zirconium, and with the balance essentially nickel, said alloy beingcharacterized in the heat treated condition by a rupture life of atleast about 200 hours when tested at 1600 F. and 25,0 0 pounds persquare inch.

20. A hot-workable, cold-workable, heat-resistant alloy particularlyadapted for service at extended periods of time under conditions of highstress and elevated temperature which comprises about 8% chromium, aboutcobalt, about 0.3% iron, about 3.7% aluminum, about 2.7% titanium, about3% molybdenum, about 0.05% zirconium, about 0.10% carbon, about 0.003%boron and the balance essentially nickel, said alloy being characterizedin the heat treated condition by a rupture life of about 517 hours whentested at 1600 F. and 25,000 pounds per square inch.

21. A hot-workable, cold-workable, heat-resistant a1- loy particularlyadapted for service at extended periods of time under conditions of highstress and elevated temperature which comprises about 8% chromium, about13% cobalt, about 3% molybdenum, about 0.12% carbon, about 3.6%aluminum, about 2.8% titanium, about 0.05 zirconium, about 0.004% boronand the balance essentially nickel, said alloy being characterized inthe heat treated condition by a rupture life of at least about 24 200hours when tested at 1600 F. and 25,000 pounds per inch. i

22. A nickel base alloy containing about 15 percent to 20 percentchromium, about 15 percent to 30 percent cobalt, about 1.5 percent to 10percent molybdenum, about 2.5 percent to 5.66 percent titanium, about.2.75 percent to 5 percent aluminum, the alloy being capable ofwithstanding an applied stress of thirty-five thousand pounds per squareinch at 1500 F. for a time in excess of two hundred hours continuously..without rupture.

23. A nickel-base alloy containing from about 5% to 20% chromium, fromabout 1% to 10% molybdenum, from about 10% to 40% cobalt, from about4.8% to 8.5% of aluminum plus titanium with the ratio of aluminum totitanium being from about 0.5 to l to 3 to l, the alloy being capable ofwithstanding an applied stress of thirty-five thousand pounds per squareinch at 1500? F. for a time in excess of 200 hours continuously, withoutrupture.

24. A nickel-base alloy containing from about 5% to 20% chromium, fromabout 1% to 10% molybdenum, up to about 40% cobalt, from about 4.5% to8.5% of aluminum plus titanium with the ratio of aluminum to titaniumbeing from about 0.5 to l to 3 to 1, the alloy being capable ofwithstanding an applied stress of thirty five thousand pounds per squareinch at 1500 F. for a time in excess of 200 hours continuously, withoutrupture.

25. Analloycontaining about 5% to 20% chromium, about 1%-to 10%molybdenum-about 10% to about 40% cobalt, about 4.8% to 8.5% of aluminumplus titanium with the ratio of aluminum to titanium being from about0.5 to 1 to 3 to 1, about 0.05% to 0.5% carbon, not more than about 5%iron, up to about 0.02% boron, up to about 0.25% zirconium and thebalance being essentially nickel, the alloy being capable ofwithstanding an applied stress of thirty-five thousand pounds per squareinch at 1500 F. for a time in excess of 200 hours continuously, withoutrupture.

26. A nickel-base alloy containing from about 5% to 20% chromium, fromabout 1% to 10% molybdenum, up to about 40% cobalt, from about 4.5% to8.5% of aluminum plus titanium with the ratio of aluminum to titaniumbeing from about 0.5 to 1 to 3 to 1, about 0.0002% to 0.009% boron, upto about 0.25% zirconium, the alloy being capable of withstanding anapplied stress of thirty-five thousand pounds per square inch at 1500"F. for a time in excess of 200 hours continuously, without rupture.

27. A nickel-base alloy containing about 15% to 20% chromium, about 15%to 30% cobalt, about 1.5%. to 10% molybdenum, about 2.5% to 5.66%titanium, about 2.75% to 5% aluminum, about 0.0002% to 0.009% boron,about 0.01% to 0.25% zirconium,.the alloy being capable of withstandingan applied stress of thirty-five thousand pounds per square inch at 1500F. for a time in excess of 200 hours continuously, without rupture.

References (Iited in the file of this patent UNITED STATES PATENTS2,150,095 Kayes Mar. 7, 1939 2,570,193 Bieber et a1 Oct. 9, 19512,575,915 Guy Nov. 20, 1951 2,688,536 Callaway et al. Sept. 7, 19542,712,498 Gresham et al. July 5, 1955 FOREIGN PATENTS 632,712 GreatBritain Dec. 5, 1949 UNITED STATES PATENT OFFICE CERTIFICATION OFCORRECTION Patent No.,2 ,i977,222 March 28 1961 Clarence George BieberIt is Hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3,, line 42 for "tunsten" read, tungsten column l5 line 32, for"having" read have line 40, for 201% read 0., 1% column 20,, line 9, for"0. 1-" read 0. 1% line 24, for "0.05" read 0.05% same column 20, line68, for 'molybednum": read molybdenum column 21, line 63, for "0051"read 005 column 23 line 17 .for aobut read about line 32, for "0.1%"read 0.07%

Signed and sealed this 29th day of August 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

24. A NICKEL-BASE ALLOY CONTAINING FROM ABOUT 5% TO 20% CHROMIUM, FROMABOUT 1% TO 10% MOLYBDENUM, UP TO ABOUT 40% COBALT, FROM ABOUT 4.5% TO8.5% OF ALUMINUM PLUS TITANIUM WITH THE RATIO OF ALUMINUM TO TITANIUMBEING FROM ABOUT 0.5 TO 1 TO 3 TO 1, THE ALLOY BEING CAPABLE OFWITHSTANDING AN APPLIED STRESS OF THIRTYFIVE THOUSAND POUNDS PER SQUAREINCH AT 1500* F. FOR A TIME IN EXCESS OF 200 HOURS CONTINUOUSLY, WITHOUTRUPTURE.